Isomerization processes are widely used by many refiners to rearrange the molecular structure of straight chain paraffinic hydrocarbons to more highly branched hydrocarbons that generally have higher octane ratings. Many isomerization processes employ a chlorinated catalyst, such as chlorinated alumina catalyst, chlorinated platinum aluminum catalyst, and the like, in a reaction zone (e.g., refers to an area including one or more reactors). The chlorinated catalyst requires a continuous addition of chloride to replace chloride removed from the surface of the catalyst and carried away in the reaction-zone effluent. Typically, a fresh feed of chloride promoter, such as perchloroethylene, is continuously introduced into a paraffin feed stream upstream from a reactor in the reaction zone. Inside the reactor, the chloride promoter decomposes to form hydrogen chloride that activates, e.g., promotes or regenerates, the catalyst by replenishing the chloride removed from the catalyst's surface.
The reaction-zone effluent generally contains a significant amount of hydrogen chloride from the continuous decomposition of chloride promoter and the removal of chloride from the surface of the catalyst. A product stream containing branched paraffins is separated from the reaction-zone effluent by removing hydrogen chloride and other light volatile hydrocarbons (e.g., C5-hydrocarbons) as a stabilizer overhead vapor stream. Because hydrogen chloride poses environmental and handling concerns, the stabilizer overhead vapor stream is continuously scrubbed with a caustic, such as sodium hydroxide, to neutralize the hydrogen chloride before removing the off-gas stream from the process. The cost of chloride promoters and caustics are relatively expensive, and many refiners would like to reduce their consumption of these components to improve their process efficiencies and reduce overall operational costs.
Accordingly, it is desirable to provide methods and apparatuses for isomerization of paraffins with reduced chloride promoter consumption and/or reduced caustic consumption to improve process efficiencies and reduce overall operational costs. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.